In the related art, for example, as disclosed in Patent Citation 1, as a tool for a cutting process of steel or cast iron, a cemented carbide tool in which plastic deformation of a cutting edge at the time of a heavy cutting process at which a cutting edge temperature is high is prevented and improvement of wear resistance is realized, by containing a hard phase of carbide such as Zr and Hf as components of cemented carbide, has been known, and also, a surface-coated carbide insert (called a coated carbide insert 1 of the related art) in which a hard coating layer is formed on a cemented carbide substrate, has been widely known.
In addition, for example, as disclosed in Patent Citation 2, a coated carbide insert (called a coated carbide insert 2 of the related art) having cemented carbide as a substrate, which contains 4% to 12% of Co, 0.3% or more of Ti, 0.5% or more of Nb, and less than 0.3% of Ta as components of cemented carbide all in weight ratio, and in which a Co enrichment region having a Co enrichment ratio of 1.20 to 3.00 and a thickness of 10 μm to 50 μm is formed in a cemented carbide surface, and cubic carbide is not included in the Co enrichment region, however, a large amount of cubic carbide is included in a lower portion of the Co enrichment region, has been known, and it has been known that the coated carbide insert 2 of the related art has high strength of the cutting edge and excellent resistance to thermal shock.    [Patent Citation 1] JP-A-2003-113437    [Patent Citation 2] JP-A-2003-205406